1. Field of the Invention
The present invention relates generally to optical systems and more particularly to folded laser system and lenses for use in such systems.
2. Technical Background
Generation of green laser light can be achieved by non-linear frequency doubling of infrared light. Typically, as illustrated in laser system of FIG. 1A, a light beam 2 from an infrared diode laser (3) is directed into a non-linear optical crystal 4, such as periodically-poled lithium niobate (PPLN) where it is converted into green light 5. In order to provide the light from the infrared diode laser to the non-linear optical crystal a lens 6 is placed between the infrared diode laser (3) and the non-linear optical crystal 4. The lens 6 intercepts the infrared light from the diode laser 3, and couples this light into the non-linear optical crystal 4.
However, because the laser systems utilize small optical waveguides that are used to confine the light in both the diode laser and the non-linear optical crystal, alignment tolerances for the components (lens, the non-linear crystal and the diode laser) are on the order of a few tenths of microns or less. This presents a challenge both for initial assembly of the laser system and for maintaining component alignment over the laser's lifetime.